body{
    min-height:100%;
}
.main-content{
    top:50px;
}
#bg-img{
    width: 100%;
    height: 100%;
    position: fixed;
    top:0;
    left: 0;
    z-index: -999;
}
.nav-bar{
    position: fixed;
    top:0;
    left:0;
    min-height: 50px;
    width: 100%;
    background: #eee;
    z-index: 99;
}
.left-div,.right-div{
    position: fixed;
    width: 250px;
    max-width: 250px;
    max-height: 900px;
    height: 860px;
    background: #eee;
}
.left-div{
    left:200px;
    top:55px;
}
.middle-div{
    position: relative;
    top:5px;
    left:85px;
    margin:0 5px 0 5px;
    width: 1205px;
    max-width: 1205px;
    min-height:860px;
    background: #eee;
}